Compressor regulator



Jan. 3.3, 1942. c. E. cox EIAL 2,259,520

COMPRESSOR REGULATOR Filed June 15, 1940 4 Sheets-Sheet l INVENT OR. (4 4/Ps/v E. Cox.

BY [ESTER A. Co44x/vs.

MAME,

ATTORNEY.

Jan. 13, 1942. c. E. cox ETAL COMPRESSOR REGULATOR 4 Sheets-Sheet 5 Filed June 15, 1940 INVENTOR. CLARENCE E. Cox.

BY [ESTER L. (cum/s4 ATTORNEY.

Jan. 13, 1942. c. E. Cox ETAL 23 5 COMPRESSOR REGULATOR 7 Filed June 15, 1940 4 Sheets-Sheet 4 INVENTOR. CLARE/v65 E. Cox.

Ass 75/? L. (cu/ vs.

ATTORNEY.

Patented Jan. 13, 1942 I 2369320 I oomnnssonnnomroa Clarence .E. Cox and Lester L. Collins, Franklin,

Pa., assignors to Chicago Pneumatic Tool Com- Y., -a corporation oi New Daily, New York, N. Jersey Application June 15, 1940, Serial No. 340,666

(Cl. zen-sol 22 Claims.

This invention relates generally to control apparatus for air or gas compressors and more particularly tomeans for obtaining a close'correspondence between the volume of fluid taken from a storage tank for use as an actuating medium and the volume of fluid supplied to the tank by the compressor.

In association with an air compressor the mechanism of the invention operates to control the admission of air to the compression cylinder of the compressor in such a manner as to increase and reduce the volume of air admitted to the cylinder, in response to the fall and rise of the air pressure within the receiver tank. Included in the mechanism of the invention is a novel inlet valve assembly comprising a principal and an auxiliary valve, the latter of which may open and the time it remains closed depending I upon the rapidity with which the receiver pressure changes This method is objectionable be-- cause it causes wide fluctuations in the power de- 'ma.nd on the actuating motor since at one instant the "compressor is working at full load and the next instant it is working at no load.

Another methid sometimes used is to throttle the intake of the compressor in accordance with the demand on the receiver. This method causes considerable heating due to'the large number of compressions that take place, and the fact that when the air is throttled there is no appreciable drop in temperature.

Still another method of unloading is that called "free air unloading. In this method the inlet I valves at one or both ends of a double acting be closed during a variable portion of the inlet stroke to reduce by a variable amount the volume of air taken into the cylinder for compression.

' The auxiliary valve may be moved to closed position at any point in the inlet stroke, the time of movement/being determined by the air pressure.

within the receiver. The effect of this method of operation is to maintain the air pressure within the receiver at a substantially constant level without wide fluctuations in power demand on the operating motor of the compressor.

The variable capacity control of this invention I represents a departure both in mechanism and mode of operation from the usual regulating apparatus of a compressor. The most common control apparatus of the prior art is one which effects step-by-step unloading of the compressor by permitting the air within the cylinder to "be dicompression cylinder are held open to allow the air to pass freely through the valves, in and out of the cylinder. This gives either full load 'or no load for a particular" end of the cylinder and causes a disturbance in the electrical system when the compressor is operated by an electric motor. Also, the horse power required to move the air back and forth through the valves represents wasted efiort, since the operation servesno useful purpose.

The method of the presentinvention, in addition to preventing wide fluctuations in power demand, presents other advantages over the methods of the prior art. In limiting the amount of air admitted to the cylinder for compression it permits operation of the compressor with a minirected into clearance pockets on the compression stroke and be re-expanded into the cylinder on the inlet stroke. These clearance pockets'are in close proximity to the cylinder and one disadvantage of this method is that the necessarily small valve, area between each pocket and the cylinder causes the air to be moved therethrough a ,at a high velocity with a resulting loss of power.

Further, the. air being compressed into the pockets at discharge pressure is at a high temperature and there is considerable cooling of the air while in the pockets since conditions are ideal for cooling, that is, the pockets are water jacketed and the air is forced against the cylinder thereof 0 be blown out the discharge valves.

at high velocity. This cooling of the air while in the clearance pockets causes a large portion of the available power to be lost.

Another'method of unloading a compressor is to close the intake completely for a few strokes mum power consumption, and insures only slight or no disturbancein the electrical system because all cylinders are working under equal loads at all times, Further, when all cylinders areworking continuously there is no chance for lubricating oil to collect in the cylinders since any excess One object of the invention is to decrease po wer consumption and .prevent wide fluctuations in power demand, in a. constant speed air compressor, through the provision ofcontrol apparatus for varying the capacity of a the compressor to equal the demand on the air receiver. I

Another object of the invention is to vary the capacity of a compression cylinder by closing the Another object of-gthe invention is to eflectclosing of the inlet valvesunder the control of air pressures within the air receiver. in such a man- I and then open it fora while, the time it remains '55 ner'as to closethevalvesdflriflt 8 pbrtion 0f e invention, in cooperative relation with a double acting compressor and an air receiver;

Fig. 2 is an enlarged view, in longitudinal section, of a portion of Fig. 1, showing in greater detail the control apparatus of that embodiment of the invention;

Fig. 3 is a view similar to Fig. 1 showing a second embodiment of the invention;

Fig. 4 is an enlarged view, in longitudinal section, of a portion of Fig. 3 showing in greater detail the control apparatus of that embodiment of the invention;

Fig. 5 is a detail view, in longitudinal section, of the control valve and associated operating means of Figs. 3 and 4, showing the operating position;

Fig. 6 is a detail view, taken substantially along the line 66 of Fig. 5, showing the adjacent ends of the control valve and its associated operating pawl, in plan; and

Figs. 7 and 8 are diagrams illustrating the pressure fluctuations in the compression cylinder of respective single and double acting compressors, during a typical inlet and compression cycle.

In the two embodiment of the invention illustrated a compressor cylinder ID, of the double acting type and of generally tandard construction, is shown in connection with the mechanism of the invention. Referring to Figsil and 3 it will be seen that a piston ll, reciprocable within the cylinder l0, forms, in cooperation with the end walls of the cylinder and an inner side walll2, a pair of piston chambers CI and C2. A series of inlet valves l3 and discharge valves H are positioned within the cylinder ill near each end thereof and, by automatic pressure responsive operation, control the flow of air to and from the chambers Cl and C2. In the operation of ,means disabled and the control valve in closed stroke and when travelling'to the left moves through a compression stroke.

Only one inlet valve II and one discharge valve H are shown in the drawings. The construction and operation of each valve in a respective series is the same as the others in the series so that a description of one will suffice for all. Thus the inlet and discharge valves shown are representative of the respective series associated with the piston chamber CI. The description to follow is directed only to a disclosure of the construction and operation of the inlet and discharge valves shown-and to a disclosure of the control mechanism associated with one series of inlet valves. The valves l3 and I4 are of the pressure responsive ring type commonly used in thi class of machine and are not illustrated in the full details of their construction. The patent to W. H. Callan No. 1,274,383, issued August 6, 1918, may be referred to for a more complete disclosure of this type of valve. Briefly, each valve represents an assembly comprising a perforated valve seat l8, a valve ring i9 and a valve keeper 2| having a projecting portion 20 in threaded engagement with the. valve, seat. Compression springs 22 (see also Figs. 2 and 4), positioned between the keeper 2| and the ring l5, press the ring against the lower surface of the seat I8 to close the perforations therein. The flow of air past each valve assembly is thus normally prevented and is permitted only when a variation in pressure on opposite sides of the assembly, of suflicient extent to force the ring l9 to open position against the tension of springs 22, occurs. The inlet and discharge valves are, of course, oppositely arranged in the cylinder l0 in order that one will" function normally to permit only the admission of air and the other function normally to permi only the discharge of air.

. its movement by any suitable means and is urged the compressor, air is drawn from the atmosoutward to ineffective or openposition by compression springs 2l positioned in recesses in the valve seat l8. In urging the ring outward the springs 24 press the ring into engagement with the tips of a set of fingers 25 which form a part of a piston assembly 26. 'At a variable point in each inlet stroke of the piston II the piston assembly. 26 is forced downward and acts to press the valve ring 23 into engagement with the outer surface of the valve seat M to cover the perforations in the seat and thereby cut off the flow of air into The chamber CI for the remainder of the inlet stroke. The point in the inlet stroke.

atwhich the piston assembly 26 moves downthe air previously admitted to chamber CI and therein and the automatic opening of the right hand setof inlet valves l3. when moving in a rightward direction this operation is reversed,

, that is, the air in chamber Cris compressed and driven therefrom while a fresh supply of air is admitted to the chamber Cl. Describing the chamber Ci, it may be said that when travelling to the right, the piston moves through an inlet movement of the piston with reference to the versely, as the receiver pressure drops, the piston assembly operates at a later point and the volume I of air admitted to the cylinder in is increased. The piston assembly 26 forms apart of both embodiments of the invention shown. the diiiference betweenthetwoembodimentslyinginthe means for initiating operation of the assembly.

Considering first that form of the invention shown in Figs. 1 and 2 and referring particularly to Fig. 2, it will be seen that the piston assembly comprises, in addition to the fingers 23, an abutment sleeve 27 formedint'egrally with the fingers 28, a rod 28 passed through the sleeve 21, and a piston head 28 secured to the upper end of the rod 28.v The lower end or the rod. 28 projects into a recess or guideway 2| formed in the projecting portion 28 of the valve keeper 2|, while a compression spring 32 surrounding the rod 28 extends into the abutment sleeve 21 to press the sleeve upward into engagement with a'collar 83 formed on the rod 28, and thereby to press the piston assembly as a whole to its upper or inefiective position. .The upper end of the rod 28 extends into a chamber 88 through which the piston head 28 reciprocates. The

3 and into which air is driven on the compression stroke of the piston II. From the passage 88' the air is conducted through a pipe 5| into a valve housing 52 where it is forced past a check valve 58 and conducted by a pipe 58 to a cham-v upon each compression stroke of the. piston ll and acts, through pipe 58, on the upper surface of diaphragm 85 to hold the valve ll in closed position with respect to the passage 38.

The control element 51 includes, in addition to th cylindrical end piece 58, an intermediate element 58, and a closure plate 8| secured to the v upper end of the element 58. The end piece 58 chamber 34 is formed in the upper end of an extension 35 which is preferably cast as an integral part of the valve seat l8. A head piece 88, secured to the upper end of the extension 85, closes the chamber 38 and forms, in cooperation with the extension 35, a space 31 through which communication is established between the chamber 84 and a pressure 'fluid conducting passage 38 also formed in the extension 85. The passage 88 is connected, by means of a pipe 88, to the receiver tank I! (Fig. 1). so that air from the receiver is conducted directly to the passage 38 from where it may flow through the space 81 to has a threaded engagement with the lower end of the element 58'and is formed with a passage 82 establishing communication between the chamber 55 in end piece 58 and a chamber 88,

. formed in the lower end of element 58 through the cooperation of end piece 58 and a plug 84 closing the lower end of the element 59 from communication with the upper end. A port 85 chamber and act on the upper surface of piston head 28 to force the piston assembly 28 to its lower or efiective position. Although the pipe 88 is shown connected to the receiver II, it will be understood that it" may, if desired. be connected to any other suitable source of pressure The flow of air through the passage 38 is controlled by a valve M movable between a seat 82 in the end of passage 38 that communicates with the space 37, and a seat 48 positioned opposite the passage 38, in the head piece 88. The valve thereof, through the valve plunger 88. when the v pressure exerted on the upper surface of the diaphragm is greater than the pressure within passage 38 the valve 8| is held on the seat 82 and prevents the flow of air from the pipe 88 and passage 88 to the chamber as. when the pressure above diaphragm 88 drops below the pressure within passage 88 valve 8| is forced from the seat 82 to the seat 88, thereby opening passage 88 and permitting the flow of actuating fluid tothe piston head 29. Upon the return of valve 8i to seat 42 the space 81- and the portion: of chamber 34 above piston head 28 are connected to atmosphere through a set ofports 87, in the.

piece 88, to which the air flows along the plunger 88. 7

Pressure above the diaphra m 55 is established by directing compressed air from the piston chamber CI to a recessed portion 88 of the closure plate 88. As shown in Fig. 2 the left hand end plate of the cylinder I8 is formed with a passage 49 communicating with the chamber Ct 8| is formed on the lower end of a plunger 88 respect to passage 82. The pressure continues to connects the chamber 83 to atmosphere and it is through the passage 82, chamber 83 and port 85 that the pressure in chamber 55 and above diaphragm 85 is reduced. The passage 82 is controlled by a valve 88 formed on the lower end of a plunger 8'! which extends upward through the intermediate element 59 and engages the lower surface of a diaphragm 88 clamped between the upper end of element 59 and closure plate 8|. A compression spring 89, seated .on the plug 88 and surrounding-the plunger 81 urges the plunger,

into engagement with the diaphragm 88 to press it upwards, whi e air conducted by way of a pipe H from th receiver H (see also Fig. l) to a recess 12 in the closure plate 8| presses the diaphragm downward. As the receiver pressure above the diaphragm 88 rises and falls the valve 88 is moved away from and towards its seat in passage 82 to increase and reduce the rate of air flow from the chamber 55.

During the compression stroke of the piston H the pressure in chamber 55 is increased to a level sumcient to force the valve 4| downward and thereby permit'the pistonassembly- 28 and valve ring 28 to rise to ineflective position. At the end of the compression stroke the supply oi air to the chamber 55 stops and, as the air escapes from the chamber along the passage 82, the pressure therein starts to drop, at a definite rate determined by the position of valve 88 with drop during the inlet stroke and, at some point during the stroke, will become insuiiicient to hold the valve 8| down, whereupon this valve will be forced oh its seat 82 and the piston assembly 28 actuated in the manner previously described to close the inlet valve for the remainder of the inlet stroke. It will be evident that the point in each inlet stroke at which th piston assembly 28 is operated is determined by the size of the vent owning between the valve 88 and passage 82 and that the position of the valve 88 with respect to the passageBZ is determined by the pressure within the receiver i1. pressure rises the pressure in chamber 55 is vented more quickly and the inlet valve closed earlier in the inlet stroke. As the receiver pressure drops, a correspondingly longer time isre- Thus, as the receiver I atmosphere, may be arranged to comm quired to vent the chamber 55 and theinlet valve.

- have also an individual piston assembly 28. A

simplified form of this principle may be used, however, requiring only one piston assembly 26 in each end of the cylinder. In this construction, th rings 23 of the remainder of the inlet valves are so balanced that they will close automatically due to the increased air velocity caused by the closing of the positively controlled valve, which thus serves as a pilot valve. It should also be understood that although the auxiliary valve normal ring 23 is said to be moved into engagement with the valve seat l8 by the piston assembly 26, it

is only necessary that the ring be positively actuated during a portion of its movement to closed position. As the valve ring approaches the seat 18 the flow of air into the piston chamber is restricted and the consequent increase in the velocity of the iiow pulls. the-ring into position against the valve seat. One control element 51 and associated control apparatus is required for each end of the cylinder in a-double acting compressor.

In Figs. 7 and 8 the pressure fluctuations within the piston chamber, caused by the closing of the inlet valve during a typical inlet stroke, are indicated diagrammatically. Fig. '7 illustrates the pressure changes in a single acting compressor, and Fig. 8 the changes in a double acting compressor. In these curves, the ordinates represent pressure and the abscissae indicate volume.

Referring to Fig. '7, the vertical broken lines Aand B may be considered to represent the opposite limits of movement of the piston II, and the horizontal broken lines C and D the normal pressure limits within the piston chamber; the line C representing the discharge pressure and the line D the intake pressure which may be atmospheric. The solid line depicts the expansion and compression of the air as the piston moves through a typical inlet and compression of air not, discharged from the piston chamber cycle. Following the solid line and starting at point E it will be seen that as the piston moves to the right on the inlet stroke the slight amount expands rapidly and shortly after the'start of the inlet stroke reaches a pressure slightly lower than the normal intake pressure. At this point, indicated as F in the drawing, the inlet valve ring I! is forced off its seat and air beginsto flow into, the piston chamber. As the piston ll continues through the inlet stroke, the inlet valve remains open and the pressure within the piston chamber is established at the normal intake level and the volume of air within the chamber increases. While this operation is taking place, however, the pressure in chamber 55, in control element 51, is dropping by reason. of vent opening 52 and, within a peri of time determined by the size of the vent op becomes insuilicient to hold control valve ll closed. At this point, indicated as G in the drawings, air passes from the receiver I1, or other pressure source, to the chamber 34 to actuate the piston assembly 26 and thereby move the auxiliary valve ring 23 75 stroke so that the remainder of this stroke is performed without effect so far as increasing the volume of air within the piston chamber is concerned. During this remaining portion of the inlet stroke the increasing size or the piston chamber allows the air already admitted thereto to expand. causing the pressure within the chamber to drop below the normal intake pressure.

As the piston I l returns leftward on the compression stroke the piston chamber is gradually reduced in size and the pressure of the air therein rises until, at a point H near the end of the compression stroke, it goes slightly above the ischarge pressure and forces open the discharge valve H. During the remainder of the compression stroke, the air is discharged from the piston chamber and directed to the receiver ll. During the compression stroke a portion bf the air in the piston chamber is also directed,

by way of p ssage 49 and pipe lines 5| and 5|, to the pressure chamber 55 and, at some point in this stroke (variable in accordance with the volume of air admitted to the piston chamber), the pressure in chamber 55 will reach a height suflicient to return valve 4| to closed position and thereby cut off the supply of actuating fluid to the piston assembly 25. When this occurs the piston assembly is immediately returned to its upper inefiective position by the spring 32, and the valve ring-23 is moved to open position by the springs 24. The pressure in chamber 55 begins 'to drop again at the end of the compression stroke.

In Fig. 8 the typical operation chosen der are identical. As long as the demand upon the air receiver remains constant the pressure fluctuations within the compression cylinder are the same throughout successive cycles of operation. Each change in the demand on the re-- ceiver, however, is reflected in a corresponding change in the volume of air admitted to the cylinder for compression.

The second or the illustrated embodiments of the invention, shown in Figs. 3 and 4, presents a means-for actuating the piston assembly 25 by hydraulic pressure. Referring particularly to Fig. 4 it will be seen that in this instance the extension 35A or the valve seat I8 is of a'more simple construction, having only a chamber ll .closed by a closure plate 13. A suitable liquid,

ll (Fig. 3) by means of an oil pump 19 and connecting pipe 8|. The pump. 19,, and its asso' ciated pressure relief valve 82, are given 'a merely diagrammatic representation here, since their construction and operation may follow any conventional practice. The pump is operated bya constantly rotating shaft 83 which may be connected directly to the main crankshaft 84, oi the compressor, or positively driven in anyv other suitable manner. Thus, as the shaft 83 rotates, oil is pumped from the reservoir 18 through the pipe 8! to the chamber 11 from where it may for i1 lustration is one in which the pressure fluctua- 'tions in each chamber of the compression cylinflow into the pipe 14 and also through a port 85 (Fig. 4) by which communication is established between the chamber TI and a chamber 86 also formed in the extension 15. The chamber 86 communicates, through a pipe 81, with the reservoir 18 so that oil flowing into this chamber is returned directly to the reservoir. A plunger valve 88 is movable within the extension 15 to an open and closed position with respect to the port 86 to control the flow of oil to the chamber 86. With the valve 88 in open position no resistance is offered to the circulation of the oil, which then flows continuously from the reservoir by way of pipe BI and back to the reservoir by way of pipe 81. The oil flows also into the pipe 14, at this time, but due to its lack of pressure is-unable to force the piston assembly 26 downward against the tension of the spring 32. With the valve 88 in closed position the free circulation of the oil back to the reservoir is interrupted and, as the pump I9 continues to force oil into the chamber 17, the pressure within pipe 14 and above'the piston head 29 increases to a point sufiicient to actuate the piston assembly 26 and close the inlet valve.

Thus, in this embodinn't of the invention, the opening and closing of the inlet valve is controlled by the plunger valve 88'which acts, in a manner to be described, to restrict the circulation of .the oil through the hydraulic system at a variable point in each inlet stroke. As shown in Figs. 4 and the valve 88 passes through the chamber 11, port 85 and chamber 86 and is formed with a reduced portion 89, adjacent these openings, about which the oil is free to pass from chamber 11 to chamber 86. In the closed position of the valve 88, shown in Fig. 5, the reduced portion 89v thereof is shifted out of the chamber I1 and a portion of larger diameter enters the port 85-and cuts oi the flow of oil to the chamber 86. In the open position of the valve, shown in Fig. 4, the reduced portion 89 extends into the chamber 11 and the return of the oil through port 85 and chamber 86 is unrestricted. The left hand end of the valve 88 (as viewed in Fig. 4) extends beyond the outer end of the extension and is formed with a head 9| which limits movement of the valve in a rightward direction. A housing 92, secured to the outer end of the extension 15, encloses the head 9| and supports a compression spring 93 which urges the head into engagement with the end extension 15 to place the valve 88 in the closed position of Fig. 5. The right hand end of the plunger valve 88 extends beyond the inner end of the extension I5 and is formed with a shoulder 94 adapted to be engaged by a pawl 95 mounted upon an eccentric disc 96 (Fig. 3) secured to the shaft 83. As the shaft 83 and eccentric 96 rotate, thepawl 95 reciprocates and, by reason of its engagement with the shoulder 98, imparts, in cooperation with the spring 93, a similar motion to the valve 88. The pawl 95 is urged downward, into engagement with the valve 88, by a light spring 98, and moves in a certain timed relation to themovement of the piston II. Slightly before the end of the compression or discharge stroke the pawl engages the shoulder 94 and moves the valve 88 forward,

. against the tension of spring 93, to open position.

The valve 88 continues to move forward during the inlet stroke but at some point during this stroke the pawl 95 is disengaged from the shoulder 94 whereupon the valve snaps back to closed position and the operation of closing the inlet valve is initiated. The means for disabling the pawl 95 resides in a cam plate 91 formed with a pair of upstanding arms .98, having inclined surfaces 99 (see also Fig. 6), between which the reduced right hand end of the valve 88 moves. The cam plate 91 is secured to the upper end of a rod I8I movable within the control element 16 to place the inclined surfaces 99 to a plurality of positions with respect to the pawl 95. Thus at some point during the forward movement of the pawl 95, the nose thereof engages the inclined surfaces 99 and, as the pawl continues to move forward, is camuned out of engagement with the shoulder 94, whereupon the valve 88 is re turned immediately to closed position by the spring 93. The variable positioning of the cam plate'91 is accomplished'against the tension of a spring I82, which urges the rod I8I downward, and is brought about through the application of receiver pressure against the lower surface of a diaphragm I83, the upper surface of which is engaged by the lower end of rod IN. The diaphragm I83 is clamped between the lower end of control element 16 and a'closure plate I84, and air from the receiver I1 is conducted to a recess I85 in the plate I84, by means of a connecting pipe I86. The rise and fall of the pressure in receiver I1 is thus reflected in a corresponding movement of the diaphragm I83 and of the cam plate 91 to advance or delay the point in the'inlet stroke at which the pawl 95 is disabled. In reading the diagrams of Figs. 7 and 8 in connection with the second embodiment of the invention, point G indicates the point in the inlet stroke, of the examples shown, at which the auxiliary inlet valve 23 closes in response to the release of valve 88.

What is claimed is:

1. A valve assembly comprising a ring valve arranged to prevent the passage of air through the assembly, a second ring valve arranged to prevent the passage of air through the assembly, a yielding means urging the first said valve to effective position, a yielding means urging the second said valve to inefiective position, and

means for moving the second said valve toward effective position.

2. A valve assembly comprising a ring valve arranged to prevent the passage of air through the assembly, a second ring-valve arranged to prevent the passage of air through the assembly, a. yielding means urging the first said valve to effective position, a yielding means urging the second said valve to ineffective position, and pressure responsive means for moving the second said valve toward effective position, said means including a piston assembly having a plurality of contact fingers engaging the second said valve. 3. A valve assembly comprising a perforated 'valve seat, a first valve positioned adjacent said valve seat on one side thereof and movable to an open and closed position with respect to the perforations therein, a second valve positioned adjacent said valve seat on the opposite side thereof. and movable to an open and closed position with respect to the perforations therein,

a yielding means urging said first valve to closed position, a yielding means urging said secondvalve to open position, and means cooperative with said second valve and movable relatively to said valve seat for moving said second valve toward closedposition.

4. A valve assembly comprising a perforated valve seat, a first valve positioned adjacent said valve seat on one side thereof and movable to an open and closed position with respect to the perforations therein a second valve positioned adjacent said valve seat on the opposite'side thereof and movable to an open and closed position with respect to the perforations therein, a yielding means urging said first valve to closed position, a yielding means urging said second valve to open position, a valve seat extension secured to said valve seat, a piston chamber formed in said valve seat extension, and a piston assemblysupported within said valve seat extension for moving said second valve toward closed position. said piston assembly comprising a piston head movable within said piston chamber and a set of contact fingers engaging said second valve.

5. In a compressor, the combination of a piston chamber, an inlet valve and a discharge valve controlling the flow of air to and from said chamber, a piston movable within said chamber through an inlet stroke and a compression stroke, during the former of which air is admitted to said chamber through said inlet valve and during the latter of which the air so admitted to the chamber is compressed and discharged through said discharge valve, a receiver to which the air discharged from said chamber is directed and stored for use as an actuating fluid, and means for closingsaid inlet valve during a variable portion of the inlet stroke to vary the volume of air adrnitted to said chamber in accordance with the varying demand on said receiver.

6. In a compressor, the combination of a piston chamber, an inlet valve and a discharge valve controlling the flow of air to and from said chamber, a piston movable within said chamber through an inlet stroke and a compression stroke, v

during the former of which air is admitted to said chamber through said inlet valve and during the latter of which the air so adm-J'ted to'the chamber is compressed and discharged through said discharge valve, a receiver to which the air discharged from said chamber is directed and stored for use as an actuating fluid, normally ineffective means for closing said inlet valve to prevent the flow of air into said chamber, and means controlled by the air pressure within said receiver for rendering said closing means effective during a portion of the inlet stroke variable in accordance with the degree of pressure within said receiver.

7. In a compressor, the combination of a piston chamber, an inlet valve assembly controlling the admission of air into said piston chamber, an auxiliary valve comprised in said inlet valve assembly for preventing the passage of air into said piston chamber, pressure responsive means for moving said auxiliary valve to closed position, a pressure fluid system including means for directing pressure fluid to said pressure responsive means, and settable means controlling the circulation of pressure fluid in said system to render said pressure fluid efiective and ineflective to actuate said pressure responsive closing means. 7

8; In a compressor, the combination of a piston chamber, a receiver to which air is directed from said piston chamber, an inlet valve assembly controlling the admission of air into said piston chamber, an auxiliary valve comprised in said inlet valve assembly for preventing the passage of air into said piston chamber, pressure responsive means for moving said auxiliary valve trolling the circulation of pressure fluid in said system to render said pressure fluid effective and ineffective to actuate said pressure responsive closing means, means for setting said settable means in position to render the pressure fluid in said system ineffective to" operate said pressure responsive closing means, and means controlled by the pressure of the air in said air receiver for disabling said last mentioned means.

9. In a compressor, the combination of a piston chamber, a receiver to which air compressed 'within said piston chamber is directed, an inlet valve assembly controlling the admission of air into said piston chamber, an auxiliaryvalve comprised in said inlet valve assembly for preventing the passage of air past said assembly, a yielding means urging said auxiliary valve to ineffective position, and means controlled by the air pressure wtihin said receiver for moving said auxiliary valve to efi'ective position.

10. In acompressor, the combination of a'pistoncharnber, an inlet valve assembly controlling the admission of air into said piston chamber, an auxiliary valve comprised in said valve assembly and movable from an open to a closed position to prevent the passage of air through said assembly, a yielding means urging said auxiliary valve to open position, pressure responsive means for moving said auxiliary valve to closed position, said pressure responsive means comprising a piston assembly having a set of contact fingers engaging said auxiliary valve, means for directing pressure fluid to said piston assembly to actuate said assembly, and means for controlling the flow of pressure fluid to said piston assembly to cut off and establish such flow alternatively.

11. In a compressor, the combination of a piston chamber, an air receiver to which air compressed within said piston chamber is directed, an inlet valve controlling the admission of air, into said piston chamber, pressure responsive means for closing said inlet valve to prevent the fiow of air into said piston chamber, a passage conducting air from said receiver to actuate said pressure responsive means, a pressure chamber to which air is directed from said piston chamber, a control valve movable in response to pressure variations between said passage and said pressure chamber to open and closed positions with respect to said passage, and means movable in response to pressure variations in said air receiver for reducing the pressure of the air in said pressure chamber at a variable rate.

12. In a compressor, the combination of a piston chamber, an air receiver to which compressed air is directed from said piston chamber, an inlet valve controlling the admission of air into said piston chamber, pressure responsive means for closing said inlet valve to prevent the flow of air into said piston chamber, a passage conducting air from said receiver to actuate said pressure responsive means, a pressure chamber to which air is directed from said piston chamber, a control valve movable in response to pressure variations between said passage and said pressure chamber to open and closed positions with respect to said passage, a vent opening said pressure chamber to atmosphere, and means movable in response to pressure variations in said receiver for varying the size of said vent to increase or reduce the' rateof reduction of pressure in said pressure chamber.

13. In a compressor,'the combination of a piston chamber, a piston movable within said chamber through an inlet stroke and a compression is directed and stored for use as an actuating fluid, an inlet valve controlling the admission of air into said piston chamber, pressure responsive means for closing 'said inlet valve to prevent the flow. of air into said chamber, a passage conducting air' from said receiver to actuate said:

pressure responsive means, a control valve movable to a closed position against the pressure of the air in said receiver to close said passage, a pressure chamber to which air is directed from said piston chamber on the compression stroke, means for applying the pressure within said pressure chamber upon said control valve to urge said control valve to closed position, a vent connecting said pressure chamber to atmosphere whereby the pressure acting on said control valve is reduced during the inlet stroke toallow said control valve to be moved to open position, and means movable in response to pressure variations in said receiver for varying the size of said vent to increase or reduce the rate of reduction of pressure in said pressure chamber and thereby advance or delay the point in the inlet stroke at which said control valve is moved to open position and said inlet valve closed.

14. In a compressor, the combination of a piston chamber, an inlet valve controlling the admission of air into said chamber, pressure responsive means for closing said inlet valve to prevent the flow of air into said chamber, a hydraulic system including means for. applying hydraulic pressure to said pressure responsive means toactuate said means, a yielding means resisting actuation of said pressure responsive means and preventing actuation of said means responsive means for closing said inlet valve to prevent the flow of air into said chamber, a hydraulic system includingmeans for applying hydraulic pressure to said pressure responsive' means to actuate said means, a yielding means resisting actuation of said pressure responsive means and preventing actuation of 'said means by the normal'pressure in said hydraulic system, meansreciprocable from and to a position restricting the free circulation of fluid in said system to increase the pressure therein above its normal level, a yielding means urging said reciprocable means to restricting position, operating means for effecting reciprocation of said reciprocable means whereby said reciprocable means reaches restricting position at a constant point in the operation of said operating means,

' and means settable to a. plurality of positions by the normal pressure in said hydraulic system,

means reciprocable from and to a position restricting the free circulation of fluid in said system to increase the pressure therein above its normal level, operating means for efiecting reciprocation of said reciprocable means, and

means for controlling the operation of said re-aciprocable means to efiect its movement to restricting position during a variable portion of the operation of said operating means.

15. In a compressor, the combination of a piston chamber, a piston movable within said chamber through an inlet stroke and a discharge stroke during the former of which air is admitted to said chamber and during the latter of which the air so admitted is compressed and discharged therefrom, an inlet valve controlling the admission of air into said chamber, pressure responsive -means for closing said inlet valve to prevent the flow of air thereby, a hydraulic system including means for applying hydraulic pressure to said pressure responsive means to actuate'said means, a yielding means resisting actuation of said pressure responsive means and preventing actuation of said means by the normal pressure in said hydraulic system, means reciprocable from and to a position restricting the free circulation of fluid in said system to increase the pressure therein above its normal level, and means for efi'ecting operation of said reciprocable means in a timed relation to the movement of said piston.

16. In a compressor, the combination of a piston chamber, an inlet valve controlling the admission of air into said chamber, pressure relative to said operating means for disabling said operating means at a variable point in the operation thereof.

17. In a compressor, the combination of a piston chamber, a piston movable within said chamber through an inlet stroke and a compression stroke during the former of which air is admitted to said chamber and during the latter of which the air so admitted to the chamber is compressed and discharged therefrom, a receiver to which the air discharged from; said chamber is directed and stored for use' as an actuating fluid, an inlet valve controlling the admission of air into said piston chamber, pressure responsive means for closing said inlet valve to prevent the flow of air into said chamber, a hydraulic system including means for applying hydraulic pressure to said pressure responsive means to actuate said means,'a yielding means resisting actuation of said pressure responsive means and preventing I actuation of said means by the normal pressure in said hydraulic system, means reciprocable from and to a position restricting the free circulation of fluid in said system to increase the pressure therein above its normal level, a yielding means urging said reciprocable means to restricting position, operating means movable in a timed relation to the movement of said piston to move said reciprocable meansfrom restricting position during the inlet stroke, means for disabling said operating means during its movement in the inlet stroke, whereupon said reciprocable means is returned to restricting position for the remainder of the inlet stroke, and means movable in response to pressure variations in said air receiver for setting said disabling means to a plurality of disabling positions relative to said operating means to advance or delay the point in the inlet stroke at which said operating means is disabled.

18. In a compressor or like machine having a positively driven air compressingpiston, the combination of a valve assembly controlling the intake of air into said compressor and comprising a control valve, an auxiliary valve controlling the passage of air through the assembly, a yielding means holding said auxiliary valve normally inefiective or in open position, actuating means for moving said auxiliary valve toward efiective or closed position,.and means operating in a. timed relation to the movement of said compressor piston for successively enabling and disabling said actuating means.

19. A compressor or like machine according to I claim 18 having a receiver for the storage of 20. In a compressor or like machine having a positively driven air compressing piston, the combination of a valve assembly controlling the intake of air into said compressor and comprising a control valve, an auxiliary valve controlling the passage of air through the assembly, a yielding means holding said auxiliary valve normally inefiective or in open position, actuating means for moving said auxiliary valve toward efiective or closed position, means for enabling and disabling said actuating means, means for initiating operation of said enabling and disabling means in a timed relation to the operation of said air compressing piston, and settable means controlling the operation of said last named means to vary the timed relation in the operations of said enabling and disabling means and of said piston.

21. In a compressor or-like machine having a positively driven air compressing piston movable through successive inlet and compression strokes, during the former of which air is admitted to the compressor and during the latter of which the air so admitted is compressed and discharged from the compressor, the combination of a re ceiver to which the air discharged from said compressor is directed and stored for use as an actuating fluid, means settable to eflective and.

normally inactive means for restricting the admission of air to the compressor, means operating in a timed relation to the movement 0! said piston for initiating operation of said restricting means, said means acting to hold said restricting means in active operation during a part of each of a series of inlet strokes of the piston to permit v the free entry of air into the compressor only during the remaining portion of an inlet stroke, and means for varying the timed relation to the operations of said initiating means and said piston to lengthen and shorten the period of free air entry in each of the series of inlet strokes.

QLARENCE E. EOYL. LESTER L. COIILINS. 

